fix(sidebar-agent): evict tool-use registry entries on tool_result

toolUseRegistry was append-only. Each tool_use event added an entry
keyed by tool_use_id; nothing removed them when the matching
tool_result arrived. Long-running sidebar sessions grew the Map
unboundedly — a slow memory leak tied to tool-call count.

Delete the entry when we handle its tool_result. One-line fix.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

browse/src/sidebar-agent.ts

@@ -367,6 +367,7 @@ async function handleStreamEvent(event: any, tabId?: number, canaryCtx?: CanaryC
           // fires, onToolResultBlock handles kill + emit.
           toolResultScanCtx.scan(toolName, text).catch(() => {});
         }
+        if (block.tool_use_id) toolUseRegistry.delete(block.tool_use_id);
       }
     }
   }